Release coating compositions and pressure sensitive adhesives are used in making pressure sensitive products such as labels, decals, tapes, and the like. The release coating composition is adhered to a paper or film substrate which is used as a release backing sheet (sometimes referred to as a protective release sheet or a release liner). The pressure sensitive adhesive is adhered to the release coating. Another paper or film substrate (sometimes referred to as a facestock) overlies the pressure sensitive adhesive. The combination of the release coating, adhesive and two substrates forms the pressure sensitive product. The pressure sensitive adhesive adheres to the release coated surface of the release backing sheet sufficiently to enable the pressure sensitive product to be handled prior to use. When the product is used, the release backing sheet is pulled off and discarded. The exposed pressure-sensitive adhesive is pressed onto a surface where the pressure sensitive product is to be placed.
The prior art techniques for applying these release coating compositions and pressure sensitive adhesives to the substrates generally involve contact coating techniques. A contact coating technique is one in which the applicator is in contact or in substantial contact with the substrate as the release coating composition or adhesive is applied. Examples of such contact coating techniques include gravure, reverse gravure, offset gravure, roller coating, brushing, knife-over roll, metering rod, reverse roll coating, doctor knife, dipping and die coating. While many of these contact coating techniques are meritorious, there are inherent problems associated with their use including the formation of wrinkles, streaks, voids and other coating defects. A non-contact coating technique, on the other hand, is one in which the applicator does not contact the substrate as the coating material is applied. An example of such a non-contact coating technique is conventional spraying. There are problems associated with conventional spraying, however, including poor deposition efficiencies and overspraying. The present invention, which involves the use of electrostatic spraying, overcomes these problems.